Western Digital RMA Service?

I wanted to get my hard drive RMA'ed but their site gives very vague details about the process. Spontaneous crashes, and strange noises leads me to conclude that my drive is faulty. Only when it reaches a certain capacity, do I experience these problems.

Warrantry verifier says I'm eligible, and I want to do chose the "Advance Replacement" method. But I want to hold off because it says on their site "For Advance Replacements, you have 30 days to return the defective product. If no defective product is returned within that time, you will be billed approximately 30 days from the date the replacement was shipped."

I'm just worried that if they don't find my drive defective, I'll get billed and I'm not trying to cheat the system in any way.

Jam it back in, in the dark.